2.5 Unreleased Songs

"Unreleased songs" are generally defined are those that have been played live 
but never officially released on CD, tape or otherwise. A quick list of TSP
songs that have not been released can be found here:
http://www.spfc.org/songs-releases/song.html?song_type=1&song_display=0|||||||||1

Another way to find unreleased songs is to use SPFC's song search feature. 
You can specify a large number of criteria to search on, in any combination,
such as whether a song has been played live or not, what band, lyrics, etc. 
Give it a shot:

SPFC's Song Search:
http://www.spfc.org/songs-releases/song_search.html